Izzy had been giving the command to throw some of the gold over the ship in order to catch up to their next target, when Jim had questioned him, saying it didn’t make sense. Of course, he began to yell,

“It is your job to follow my f-fucking orders…”

But there are tears in his eyes, and his voice cracks and breaks at the end. His unhealthy relationship with Blackbeard is clearly straining and killing him from the inside out. He just wants to be loved. He’s so damn stressed all the time.